Glycosyl transferase family 64 domain. Members of this family catalyze the transfer reaction of N-acetylglucosamine and N-acetylgalactosamine from the respective UDP-sugars to the non-reducing end of [glucuronic acid]beta 1-3[galactose]beta 1-O-naphthalenemethanol, an acceptor substrate analog of the natural common linker of various glycosylaminoglycans. They are also required for the biosynthesis of heparan-sulphate.